Abstract
Abstract. New-particle formation in the plumes of coal-fired power plants and other anthropogenic sulfur sources may be an important source of particles in the atmosphere. It remains unclear, however, how best to reproduce this formation in global and regional aerosol models with grid-box lengths that are tens of kilometres and larger. Based on the results of the System for Atmospheric Modelling (SAM), a large-eddy simulation/cloud-resolving model (LES/CRM) with online two-moment aerosol sectional (TOMAS) microphysics, we have developed a computationally efficient, but physically based, parameterization that predicts the characteristics of aerosol formed within sulfur-rich plumes based on parameters commonly available in global- and regional-scale models. Given large-scale mean meteorological parameters ((1) wind speed, (2) boundary-layer height and (3) downward shortwave radiative flux), (4) emissions of SO2 and (5) NOx from the source, (6) mean background condensation sink, (7) background SO2 and (8) NOx concentrations, and (9) the desired distance from the source, the parameterization will predict (1) the fraction of the emitted SO2 that is oxidized to H2SO4, (2) the fraction of that H2SO4 that forms new particles instead of condensing onto pre-existing particles, (3) the mean mass per particle of the newly formed particles, and (4) the number of newly formed particles per kilogram SO2 emitted. The parameterization we describe here should allow for more accurate predictions of aerosol size distributions and a greater confidence in the effects of aerosols in climate and health studies.
Highlights
It is well known that the size of atmospheric aerosols strongly impacts the magnitude of their direct radiative effect (Charlson et al, 1992) and their ability to act as cloud condensation nuclei (CCN) (Dusek et al, 2006), thereby increasing cloud reflectivity and lifetime (Albrecht, 1989; Twomey, 1974)
The purpose of the P6 parameterization is to predict the fraction of emitted SO2 that is oxidized in the plume, whether or not a significant number of new particles are nucleated, the number of new particles nucleated per kg SO2 emitted (Nnew, [#/kg SO2]), the mean mass per particle of the new particles (Mm, [kg]), and the fraction of the H2SO4 formed within the plume that comprises new particles
We describe the predicting particles produced in power-plant plumes (P6) parameterization: a physically based, but computationally efficient, parameterization that predicts the characteristics of aerosol formed in sulfur-rich plumes based on variables that are commonly available in global- and regional-scale models
Summary
It is well known that the size of atmospheric aerosols strongly impacts the magnitude of their direct radiative effect (Charlson et al, 1992) and their ability to act as cloud condensation nuclei (CCN) (Dusek et al, 2006), thereby increasing cloud reflectivity and lifetime (Albrecht, 1989; Twomey, 1974). The study of Wang and Penner (2009), which included organic matter, black carbon, and dust, varied the fraction of SO2 converted to sub-grid sulfate over a smaller range (0 to 2 %), and found that CCN(0.2 %) more than doubled over polluted areas They found that CCN(0.2 %) increased by 23 to 53 % averaged over global boundary layer and that the aerosol indirect effect radiative forcing increased by 11 to 31 % (depending on the grid-resolved nucleation scheme used in the boundary layer).
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